The present invention relates generally to electric power conversion apparatuses and methods, and more particularly to electric power conversion apparatuses and methods adapted to be electrically connected to a plurality of power supplies.
Japanese Patent Application Publication No. 2002-118981 (JP2002-118981) shows an electric power conversion system which employs a fuel cell as a main power supply and a battery as a sub power supply to drive an electric motor. While the fuel cell is connected electrically and directly to the motor, the battery is electrically connected to the motor via a DCDC (Direct Current to Direct Current) converter. The output voltage of the DCDC converter is controlled in order to improve the output efficiency of the power supplies.